This invention relates to pneumatic tires for heavy duty use comprising a radial carcass and two bead portions each reinforced by a bead core, with the bead portion comprising a rubber apex strip of a substantially triangular cross-section extending radially outwardly from the bead core and having a Shore A Hardness (ASTM D1415) greater than 70, and with the radial carcass comprising at least one cord reinforced elastomeric ply, extending between the bead cores and passing around each bead core from the axially inner side tothe axially outer side, the end portions of the carcass ply turn-up being encased in a pair of non-fiber cord reinforced gum strips.
The bead portion of a radial truck tire in use is subject to cyclic stresses and strains as the tread of the tire passes through the footprint. It is well known in the tire art that one of the most important stress points in the bead area of a tire occurs around the ply endings of the carcass plies. These stresses and strains can cause cracking and ply ending separation, that is separation of the carcass ply turn-up from the surrounding rubber compound. This separation can eventually lead to a mode of failure of the tire which is known in the trade as `bead area failure`.